Touch panel

ABSTRACT

A touch panel includes a first electrode formed of first thin metal wires arranged in the transmissive region and a second electrode insulated from the first electrode and formed of second thin metal wires arranged to intersect the first thin metal wire in the transmissive region, in which the second thin metal wires is arranged on the side opposite to the viewing side than the first thin metal wires.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of US application No. U.S. Ser. No.15/683,013 filed on Aug. 22, 2017, which claims priority under 35 U.S.C.§ 119(a) to PCT International Application No. PCT/JP2015/077555 filed onSep. 29, 2015, and Japanese Patent Application No. 2015-057648 filed onMar. 20, 2015. Each of the above application(s) is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a transparent conductive film and amethod of producing the same, and particularly to a transparentconductive film used for a touch panel or the like and a method ofproducing the same.

In addition, the present invention relates to a touch panel using atransparent conductive film.

2. Description of the Related Art

In recent years, in various electronic devices such as a portableinformation device, a touch panel that can be used in combination with adisplay device such as a liquid crystal display device and performs aninput operation to an electronic device by touching a screen has comeinto wide use.

For example, JP2013-206315A discloses a touch panel in which a firstelectrode formed of a stripped copper wiring is formed on a frontsurface of a transparent insulating substrate and a second electrodeformed of a stripped copper wiring is formed on a rear surface of thetransparent insulating substrate in a direction orthogonal to the copperwiring of the first electrode.

In the touch panel, specular reflection is reduced and contrast isimproved by forming a blackened layer formed of a black copper oxidecoating film at the end portion of the copper wiring which becomes aviewing side, in the case in which the touch panel is mounted in adisplay device or the like, out of both the copper wirings of the firstelectrode and the copper wiring of the second electrode. For example, inthe case in which the first electrode formed on the front surface of thetransparent insulating substrate is arranged on the viewing side, ablackened layer is formed at each of the end portion of the copperwiring of the first electrode on the side opposite to the transparentinsulating substrate and the end portion of the copper wiring of thesecond electrode on the side close to the transparent insulatingsubstrate.

SUMMARY OF THE INVENTION

In order to prevent the presence of a copper wiring having lightshielding properties from being visually recognized and to reduce moiregenerated due to the interference of a pixel of a display device inwhich a touch panel is mounted with the copper wiring, the copper wiringwhich forms a first electrode and a second electrode needs to be thinnedto a width of about 1 to 5 μm.

Such a copper wiring can be obtained by forming a copper foil on atransparent insulating substrate, and patterning the copper foil by aphotolithography method using a resist. In this case, it is necessary toperform wet etching by causing the resist to adhere to the copper foilwith high adhesion to perform patterning of a line width of about 1 to 5μm with high accuracy. In this case, as shown in FIG. 9, copper wirings2 and 3 each having a reversely tapered cross-sectional shape in which aline width W2 of the copper wiring on a side close to a transparentinsulating substrate 1 is smaller than a line width W1 of the copperwiring on a side opposite to the transparent insulating substrate 1 areformed. At each of the end portions of the copper wirings 2 and 3 on theviewing side, a blackened layer 4 is formed.

However, as shown in FIG. 9, the stripped copper wirings 2 and 3 eachhaving a line width of about 1 to 5 μm are formed on a front surface 1Aand a rear surface 1B of the transparent insulating substrate 1. Forexample, in the case in which the transparent insulating substrate 1 isobserved vertically from the front surface 1A side, there is a problemof viewing angle dependency in which the metallic luster of the copperwiring is noticeable according to the viewing angle in the case in whichthe transparent insulating substrate is oblique viewed.

It is found that this is because, since the respective copper wirings 2and 3 have a reversely tapered cross-sectional shape, a side surface 3Cof the copper wiring 3 formed on the rear surface 1B of the transparentinsulating substrate 1 is easily viewed from the viewing side, andstrong reflected light on the side surface 3C is changed according tothe viewing angle.

As in the end portions of the copper wirings 2 and 3 on the viewingside, in the case in which the blackened layer 4 is formed, reflectioncan be reduced. However, it is difficult to form the blackened layer 4on the side surface 3C of the copper wiring 3 due to the productionprocess.

The present invention has been made to solve the above problems of therelated art, and an object thereof is to provide a transparentconductive film capable of ensuring excellent visibility with lowviewing angle dependency while forming an electrode formed of thin metalwires on each of a viewing side and a side opposite to the viewing side.

Another object of the present invention is to provide a method ofproducing a transparent conductive film capable of obtaining such atransparent conductive film.

Still another object of the present invention is to provide a touchpanel using such a transparent conductive film.

A transparent conductive film according to the present invention is atransparent conductive film having a transmissive region comprising: atransparent insulating substrate having a first surface that is directedto a viewing side and a second surface that is directed to a sideopposite to the viewing side; a first electrode formed of first thinmetal wires arranged on the first surface of the transparent insulatingsubstrate in the transmissive region; and a second electrode insulatedfrom the first electrode and formed of second thin metal wires arrangedon the second surface of the transparent insulating substrate tointersect the first thin metal wire in the transmissive region, in whichthe first thin metal wire has a first front surface being directed tothe viewing side and having a line width W1A and a first back surfacebeing directed to the side opposite to the viewing side and having aline width W1B, the second thin metal wire has a second front surfacebeing directed to the viewing side and having a line width W2A and asecond back surface being directed to the side opposite to the viewingside and having a line width W2B, and the line widths W1A, W1B, W2A, andW2B are in a range of 0.5 to 10 μm, and the line width W1A is largerthan the line width W1B and the line width W2A is larger than the linewidth W2B.

It is preferable that the line widths W1A and W2A satisfy a relationshipof 0≤W1A−W2A≤0.3×W1A.

It is preferable that the line widths W1A, W1B, W2A, and W2B satisfy arelationship of W2A−W2B<W1A−W1B. In this case, it is more preferablethat a thickness H2 of the second thin metal wire is larger than athickness H1 of the first thin metal wire.

It is preferable that the line width W1A is 1.5 μm or more and 5 μm orless, and the thickness H1 of the first thin metal wire and thethickness H2 of the second thin metal wire are 0.5 μm or more and 3 μmor less.

In addition, the first front surface of the first thin metal wire andthe second front surface of the second thin metal wire may be blackenedlayers.

It is preferable that the first thin metal wire and the second thinmetal wire are formed of copper.

A method of producing a transparent conductive film according to thepresent invention is a method of producing the transparent conductivefilm comprising: forming a first metal layer on the first surface of thetransparent insulating substrate and forming a second metal layer on thesecond surface of the transparent insulating substrate; forming apatterned first resist layer on a surface of the first metal layer andforming a patterned second resist layer on a surface of the second metallayer; performing an adhesion reinforcing treatment for furtherenhancing adhesion between the first metal layer and the first resistlayer than between the second metal layer and the second resist layer byreinforcing adhesion between the first metal layer and the first resistlayer; and forming the first thin metal wire and the second thin metalwire by performing wet etching on the first metal layer and the secondmetal layer respectively or simultaneously.

Another method of producing a transparent conductive film according tothe present invention is a method of producing the transparentconductive film comprising: forming the first thin metal wire on thefirst surface of the transparent insulating substrate; forming thesecond thin metal wire on a surface of a transfer substrate; andtransferring the second thin metal wire to the second surface of thetransparent insulating substrate from the transfer substrate.

A touch panel according to the present invention is a touch panel usingthe transparent conductive film. As the touch panel, a projection typeelectrostatic capacitance touch panel that can detect multi-touch ispreferable.

According to the present invention, since the first thin metal wirearranged on the first surface of the transparent insulating substratehas the first front surface being directed to the viewing side andhaving the line width W1A and the first back surface being directed tothe side opposite to the viewing side and having the line width W1B, thesecond thin metal wire arranged on the second surface of the transparentinsulating substrate has the second front surface being directed to theviewing side and having the line width W2A and the second back surfacebeing directed to the side opposite to the viewing side and having theline width W2B, the line widths W1A, W1B, W2A, and W2B are in a range of0.5 to 10 μm, the line width W1A is larger than the line width W1B andthe line width W2A is larger than the line width W2B, it is possible toensure excellent visibility with low viewing angle dependency whileforming an electrode formed of thin metal wires on each of the viewingside and the side opposite to the viewing side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view showing a touch panel accordingto Embodiment 1 of the present invention.

FIG. 2 is a plan view showing a transparent conductive film used for thetouch panel according to Embodiment 1.

FIG. 3 is a partial plan view showing a detection electrode of thetransparent conductive film used for the touch panel according toEmbodiment 1.

FIG. 4 is a partial cross-sectional view showing a first thin metal wireand a second thin metal wire of the transparent conductive film used forthe touch panel according to Embodiment 1.

FIGS. 5A to 5F are cross-sectional views showing the step procedure of amethod of producing the touch panel according to Embodiment 1.

FIGS. 6A to 6C are cross-sectional views showing the step procedure ofanother method of producing the touch panel according to Embodiment 1.

FIG. 7 is a partial cross-sectional view showing a first thin metal wireand a second thin metal wire of a transparent conductive film used for atouch panel according to Embodiment 2.

FIG. 8 is a partial plan view showing a detection electrode of atransparent conductive film used for a touch panel according toEmbodiment 3.

FIG. 9 is a partial cross-sectional view showing a first thin metal wireand a second thin metal wire of a transparent conductive film used for aconventional touch panel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 shows a configuration of a touch panel 11 according to Embodiment1 of the present invention. The touch panel 11 has a transparentinsulating cover panel 12 having a flat plate shape, and the transparentconductive film 13 is bonded to a surface of the cover panel 12 on aside opposite to a viewing side with a transparent adhesive 14. In thetransparent conductive film 13, a conductive member 32 is formed on eachof both surfaces of the transparent insulating substrate 31. Inaddition, as shown in FIG. 1, for the purpose of flattening orprotecting the conductive member 32, a transparent protective layer 33may be formed on both surfaces of the transparent insulating substrate31 so as to cover the conductive member 32.

As the material for the cover panel 12, tempered glass, polycarbonate(PC), a polymethyl methacrylate resin (PMMA), or the like can be usedand a thickness thereof is preferably 0.1 to 1.5 mm.

As the material for the transparent insulating substrate 31, glass,polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acycloolefin polymer (COP), a cyclic olefin copolymer (COC), or the likecan be used, and a thickness thereof is preferably 20 to 200 μm.

As shown in FIG. 2, a transmissive region S1 is partitioned in thetransparent conductive film 13, and a peripheral region S2 ispartitioned on the outside of the transmissive region S1. On the frontsurface 31A of the transparent insulating substrate 31, a plurality offirst electrodes 34 that respectively extend in a first direction D1,are arranged in parallel in a second direction D2 orthogonal to thefirst direction D1, and are formed of the conductive member 32 is formedin the transmissive region S1, and a plurality of first peripheralwirings 35 that are connected to the plurality of first electrodes 34and are formed of the conductive member 32 is mutually closely arrangedin the peripheral region S2.

Similarly, on the rear surface 31B of the transparent insulatingsubstrate 31, a plurality of second electrodes 36 that respectivelyextend in the second direction D2, are arranged in parallel in the firstdirection D1, and are formed of the conductive member 32 is formed inthe transmissive region S1, and a plurality of second first peripheralwirings 37 that are connected to the plurality of second electrodes 36and are formed of the conductive member 32 is mutually closely arrangedin the peripheral region S2.

FIG. 3 shows intersections of the first electrodes 34 and the secondelectrodes 36. The first electrodes 34 arranged on the front surface 31Aof the transparent insulating substrate 31 are formed with a meshpattern formed by the first thin metal wire 38, and the secondelectrodes 36 arranged on the rear surface 31B of the transparentinsulating substrate 31 are also formed with a mesh pattern formed bythe second thin metal wire 39. In the intersection of the firstelectrode 34 and the second electrode 36, in the case in which thetransparent conductive film is viewed from the viewing side, the firstthin metal wire 38 and the second thin metal wire 39 are arranged so asto intersect each other. In FIG. 3, in order to easily distinguish thefirst thin metal wire 38 and the second thin metal wire 39, the secondthin metal wire 39 is indicated by a dotted line but is actually formedof a connected wire like the first thin metal wire 38.

As the shape of the mesh pattern, a pattern in which the same mesh isrepeatedly arranged as shown in FIG. 3 is preferable and a diamond shapeis particularly preferable as the mesh shape. However, the mesh shapemay be a parallelogram shape, a square shape, a rectangular shape, oranother polygonal shape. A distance between the centers of the meshes(mesh pitch) is preferably 100 to 600 μm from the viewpoint ofvisibility. It is preferable that a mesh pattern formed by the firstthin metal wire 38 and a mesh pattern formed by the second thin metalwire 39 have the same shape. Further, as shown in FIG. 3, the meshpattern formed by the first thin metal wire 38 and the mesh patternformed by the second thin metal wire 39 are arranged to be shifted by adistance corresponding to half of the mesh pitch and are preferablyarranged to form a mesh pattern with a half mesh pitch from the viewingside from the viewpoint of visibility. As another embodiment, the meshshape may be a random pattern.

In addition, a dummy mesh pattern insulated from the electrodesrespectively formed of the first thin metal wire 38 and the second thinmetal wire 39 may be provided between the first electrodes 34 adjacentto each other and between the second electrodes 36 adjacent to eachother. The dummy mesh pattern is preferably formed in the same meshshape as the mesh pattern that forms the electrode.

As shown in FIG. 4, the first thin metal wire 38 of the first electrode34 arranged on the front surface 31A of the transparent insulatingsubstrate 31 has a first front surface 38A that is directed to theviewing side and a first back surface 38B that is directed to the sideopposite to the viewing side, and has a shape in which a line width W1Aof the first front surface 38A is larger than a line width W1B of thefirst back surface 38B, a so-called reversely tapered cross-sectionalshape.

On the other hand, the second thin metal wire 39 of the second electrode36 arranged on the rear surface 31B of the transparent insulatingsubstrate 31 has a second front surface 39A that is directed to theviewing side and a second back surface 39B that is directed to the sideopposite to the viewing side, and has a shape in which a line width W2Bof the second back surface 39B is smaller than a line width W2A of thesecond front surface 39A, a so-called forward tapered cross-sectionalshape.

That is, the line widths W1A and W1B of the first thin metal wire 38 andthe line widths W2A and W2B of the second thin metal wire 39 satisfy arelationship ofW1B<W1A and W2B<W2A  (1).

In addition, the line widths W1A, W1B, W2A, and W2B of the first thinmetal wire 38 and the second thin metal wire 39 are all set to be in arange of 0.5 to 10 μm so that the first thin metal wire and the secondthin metal wire are hardly visually recognized.

With this configuration, a side surface 39C of the second thin metalwire 39 arranged on the rear surface 31B of the transparent insulatingsubstrate 31 is hardly viewed and thus the viewing angle dependency ofmetallic luster of the first electrode 34 and the second electrode 36 isimproved.

In addition, a blackened layer 40 is formed on each of the first frontsurface 38A of the first thin metal wire 38 on the viewing side and thesecond front surface 39A of the second thin metal wire 39 on the viewingside. The blackened layer 40 is provided to reduce specular reflectionon the first front surface 38A of the first thin metal wire 38 and thesecond front surface 39A of the second thin metal wire 39. It isdifficult to form the blackened layer 40 on the side surface 38C of thefirst thin metal wire 38 and the side surface 39C of the second thinmetal wire 39, but it is preferable that the blackened layer 40 isformed on the front surfaces.

As the material for the first thin metal wire 38 and the second thinmetal wire 39, metals such as copper, silver, aluminum, gold, andmolybdenum or alloys thereof may be used and a film thickness thereof ispreferably 0.1 to 5 μm. Among these, copper is preferable from theviewpoint of a low resistance value, stability, and costs.

In FIG. 4, the transparent insulating substrate 31 and the first thinmetal wire 38 or the second thin metal wire 39 are directly in contactwith each other. However, one or more layers of functional layers, suchas an adhesion reinforcing layer, an undercoat layer, or a hard coatlayer, can be formed between the transparent insulating substrate 31 andthe first thin metal wire 38 or the second thin metal wire 39.

For the blackened layer 40, an oxide including copper is preferablyused, and copper oxide (II) (CuO), CuO—Cr₂O₃, CuO—Fe₃O₄—Mn₂O₃,CuO—Fe₂O₃—Cr₂O₃, and the like may be used. As other materials, blackiron oxide (Fe₃O₄), titanium black, nickel, chromium or the like may beused and a film thickness thereof is preferably 0.01 to 0.4 μm.

In addition, in the case in which light shielding members having thesame line width are respectively arranged on the front and rear surfacesof a transparent plate and the transparent plate is observed from thefront surface side, the light shielding member on the rear surface sideis viewed using light refracted on the front surface of the transparentplate, and thus, it is found that the width of the light shieldingmember arranged on the rear surface looks larger than the width of thelight shielding member arranged on the front surface.

Therefore, it is preferable that the line width W1A of the first frontsurface 38A of the first thin metal wire 38 arranged on the frontsurface 31A of the transparent insulating substrate 31 is set to have avalue slightly larger than the line width W2A of the second frontsurface 39A of the second thin metal wire 39 arranged on the rearsurface 31B of the transparent insulating substrate 31 in advance.

However, in order to prevent the presence of the first thin metal wire38 and the second thin metal wire 39 from being noticeable due to adifference in line width between the first thin metal wire 38 and thesecond thin metal wire 39 in the case in which the transparentconductive film is viewed from the viewing side, a difference betweenthe line width W1A of the first front surface 38A of the first thinmetal wire 38 and the line width W2A of the second front surface 39A ofthe second thin metal wire 39 (W1A−W2A) is desirably equal to or lessthan a value 0.3 times the line width W1A. That is, it is desirable thatthe line widths W1A and W2A satisfy a relationship of0≤W1A−W2A≤0.3×W1A  (2).

By respectively arranging such first thin metal wire 38 and second thinmetal wire 39 on the front surface 31A and on the rear surface 31B ofthe transparent insulating substrate 31, out of the front surface 31Aand the rear surface 31B of the transparent insulating substrate 31, theline width W1A of the first front surface 38A of the first thin metalwire 38 on the viewing side arranged on the front surface 31A positionedon the viewing side is set to be equal to the line width W2A of thesecond front surface 39A of the second thin metal wire 39 on the viewingside arranged on the rear surface 31B positioned on the side opposite tothe viewing side or is set to have a value slightly larger than the linewidth W2A. Thus, in the case in which the transparent conductive film 13is observed from the viewing side, the first thin metal wire 38 on thefront surface 31A of the transparent insulating substrate 31 and thesecond thin metal wire 39 on the rear surface 31B seem to have the sameline width. Accordingly, the presence of the mesh pattern of the firstelectrode 34 formed of the first thin metal wire 38 and the secondelectrode 36 formed of the second thin metal wire 39 is hardly visuallyrecognized and thus the visibility of the transmissive region S1 of thetransparent conductive film 13 is improved.

As a particularly preferable range, the line width W1A is slightlylarger than the line width W2A, and a difference between the line widthsis preferably 0.02 μm or more and a relationship of 0.02μm≤W1A−W2A≤0.3×W1A is satisfied.

In addition, in the case in which the transparent conductive film isviewed from the viewing side, the tapered shape of the side surface 39Cof the second thin metal wire 39 having a forward taperedcross-sectional shape that is arranged on the rear surface 31B of thetransparent insulating substrate 31 becomes loose, and in the case inwhich the transparent conductive film 13 is obliquely viewed, there is ahigh possibility that reflected light may be observed on the sidesurface 39C.

It is desirable that a difference between the line width W2A of thesecond front surface 39A and the line width W2B of the second backsurface 39B of the second thin metal wire 39 (W2A−W2B) is smaller than adifference between the line width W1A of the first front surface 38A andthe line width W1B of the first back surface 38B of the first thin metalwire 38 (W1A−W1B) so that the side surface 39C of the second thin metalwire 39 on the rear surface 31B side of the transparent insulatingsubstrate 31 is hardly viewed. That is, it is desirable that the linewidths W1A and W1B of the first thin metal wire 38 and the line widthsW2A and W2B of the second thin metal wire 39 satisfy a relationship ofW2A−W2B<W1A−W1B  (3).

In this manner, the influence of reflected light according to theviewing angle can be further reduced and thus viewing angle dependencycan be more effectively reduced.

The first thin metal wire 38 having a reversely tapered cross-sectionalshape and the second thin metal wire 39 having a forward taperedcross-sectional shape can be formed by performing wet etching on metallayers of copper or the like respectively formed on both surfaces of thetransparent insulating substrate 31. However, in order to realize theconfiguration represented by Expression (3), it is preferable that athickness H2 of the second thin metal wire 39 has a larger value than athickness H1 of the first thin metal wire 38. This is because, in thecase in which metals having different thicknesses are subjected to wetetching simultaneously, the time during which the metal having a smallerthickness is over-etched becomes longer, a reversely tapered shape istightly formed, and thus, the shape satisfying the above condition iseasily formed.

Specifically, it is desirable for the transparent conductive film 13used for the touch panel 11 to set the line width W1A of the first frontsurface 38A of the first thin metal wire 38 to 1.5 μm or more and 5 μmor less and to set the thickness H1 of the first thin metal wire 38 andthe thickness H2 of the second thin metal wire 39 to 0.5 μm or more and3 μm or less. By setting the thicknesses of the first thin metal wire 38and the second thin metal wire 39 to 0.5 μm or more and 3 μm or less, athin metal wire having a line width of 1.5 μm or more and 5 μm or lessis easily formed. Particularly, by setting the thickness of the thinmetal wire to a value equal to or less than half of the line width, athin metal wire is easily formed by performing wet etching on a metalwire having a fine line width of 5 μm or less. Further, it is preferablethat the line width W1A of the first front surface 38A of the first thinmetal wire 38 is 2 μm or more and 4 μm or less, and the thickness H1 ofthe first thin metal wire 38 and the thickness H2 of the second thinmetal wire 39 are 0.5 μm or more and 2 μm or less in consideration ofproduction suitability.

The blackened layer 40 for reducing specular reflection can be formed ofcopper oxide, in the case of using copper as the material for formingthe first thin metal wire 38 and the second thin metal wire 39, forexample.

The formation of the blackened layer 40 reduces specular reflection onthe first front surface 38A of the first thin metal wire 38 and thesecond front surface 39A of the second thin metal wire 39 that arerespectively positioned on the viewing side so as to improve contrast.

The transparent conductive film 13 is produced by forming the conductivemember 32 including the first electrode 34 and the first peripheralwiring 35 on the front surface 31A of the transparent insulatingsubstrate 31 and forming the conductive member 32 including the secondelectrode 36 and the second peripheral wiring 37 on the rear surface 31Bof the transparent insulating substrate 31.

The conductive member 32 can be formed as follows.

For example, as shown in FIG. 5A, a blackened layer 41 formed of copperoxide is formed on the rear surface 31B of the transparent insulatingsubstrate 31 and then a first metal layer 42 and a second metal layer 43each formed of copper are formed on the front surface 31A of thetransparent insulating substrate 31 and on the blackened layer 41 of therear surface 31B. Further, a blackened layer 44 formed of copper oxideis formed on the first metal layer 42 of the front surface 31A of thetransparent insulating substrate 31.

Next, as shown in FIG. 5B, a first resist layer 45 and a second resistlayer 46 are respectively formed on the blackened layer 44 of the frontsurface 31A of the transparent insulating substrate 31 and the secondmetal layer 43 of the rear surface 31B, and as shown in FIG. 5C, thefirst resist layer 45 and the second resist layer 46 are respectivelysubjected to pattern exposure through a first exposure mask 47 and asecond exposure mask 48 and developed. As shown in FIG. 5D, thepatterned first resist layer 45 and second resist layer 46 arerespectively patterned.

At this time, it is preferable that both surfaces of the first resistlayer 45 and the second resist layer 46 are exposed simultaneously. Thepattern of the first thin metal wire 38 and the pattern of the secondthin metal wire 39 can be aligned with high accuracy by simultaneousexposing both surfaces.

Then, as shown in FIG. 5E, only the first resist layer 45 on the frontsurface 31A side of the transparent insulating substrate 31 is subjectedto an annealing treatment or the like using a halogen lamp or the likeand adhesion between the first metal layer 42 and the blackened layer44, and the first resist layer 45 is reinforced to further enhancingadhesion between the first metal layer and the first resist layer thanthe second metal layer 43 and the second resist layer 46.

In this state, in the case in which the first metal layer 42 and thesecond metal layer 43 are respectively subjected to wet etching using anetching solution, since the first resist layer 45 is firmly bonded tothe front surface 31A side of the transparent insulating substrate 31,the etching solution is prevented from permeating between the firstmetal layer 42 and the blackened layer 44, and the first resist layer 45and a portion that is close to the transparent insulating substrate 31is etched more than a portion that is directed to the first resist layer45 in the first metal layer 42 as the etching time elapses. Thus, afirst thin metal wire 38 having a reversely tapered shape is formed asshown in FIG. 5F.

On the other hand, since the second resist layer 46 has a relatively lowadhesion on the rear surface 31B of the transparent insulating substrate31, the etching solution permeates between the second metal layer 43 andthe second resist layer 46 and a portion that is directed to the secondresist layer 46 is etched more than a portion close to the transparentinsulating substrate 31 in the second metal layer 43 as the etching timeelapses. Thus, a second thin metal wire 39 having a forward taperedshape is formed as shown in FIG. 5F.

Then, the transparent conductive film 13 having the structure shown inFIG. 4 can be obtained by removing the first resist layer 45 and thesecond resist layer 46.

Alternatively, the conductive member 32 can be formed as follows.

First, as in the method shown in FIGS. 5A to 5F, a first metal layerformed of copper is formed on the front surface 31A of the transparentinsulating substrate 31, and then a blackened layer formed of copperoxide is formed on the first metal layer. A patterned resist is formedon the blackened layer to perform wet etching. Then, as shown in FIG.6A, a first thin metal wire 38 having a reversely tapered shape isformed on the front surface 31A of the transparent insulating substrate31.

Further, a release layer 50 is formed on the surface of the transfersubstrate 49 in the same manner, and then a second metal layer formed ofcopper and a blackened layer formed of copper oxide are sequentiallyformed on the release layer 50. A patterned resist is formed on theblackened layer to perform wet etching. Thus, as shown in FIG. 6A, asecond thin metal wire 39 having a reversely tapered shape is formed onthe release layer 50.

As shown in FIG. 6B, the second thin metal wire 39 formed on the surfaceof the transfer substrate 49 is attached to the rear surface 31B of thetransparent insulating substrate 31 through a pressure sensitiveadhesive layer and transferred to the transparent insulating substrateand then as shown in FIG. 6C, the transfer substrate 49 and the releaselayer 50 are separated from the second thin metal wire 39. Thus, thesecond thin metal wire 39 having a forward tapered shape is arranged onthe rear surface 31B of the transparent insulating substrate 31.

Embodiment 2

The transparent conductive film 13 used for the touch panel 11 ofEmbodiment 1 has the blackened layers 40 respectively formed on thefirst front surface 38A of the first thin metal wire 38 on the viewingside and on the second front surface 39A of the second thin metal wire39 on the viewing side, but the present invention is not limitedthereto. For example, as shown in FIG. 7, the first thin metal wire 38and the second thin metal wire 39 may not have the blackened layers 40.

Even in this case, as long as all of the line widths W1A and W1B of thefirst thin metal wire 38 and the line widths W2A and W2B of the secondthin metal wire 39 are set to be in a range of 0.5 to 10 μm and satisfythe above relationship represented by Expression (1), excellentvisibility with low viewing angle dependency can be ensured.

In addition, the line width W1A of the first thin metal wire 38 and theline width W2A of the second thin metal wire 39 further satisfy theabove relationship represented by Expression (2) and thus visibility canbe further improved. As long as the line widths W1A and W1B of the firstthin metal wire 38 and the line widths W2A and W2B of the second thinmetal wire 39 satisfy the above relationship represented by Expression(3), viewing angle dependency can be further reduced.

Embodiment 3

In Embodiments 1 and 2, as shown in FIG. 3, the first thin metal wire 38of the first electrode 34 arranged on the front surface 31A of thetransparent insulating substrate 31 and the second thin metal wire 39 ofthe second electrode 36 arranged on the rear surface 31B of thetransparent insulating substrate 31 respectively have a mesh pattern,but the present invention is not limited thereto. For example, thetransparent conductive film can also be configured such that as shown inFIG. 8, the first electrodes 34 are formed of a plurality of first thinmetal wires 58 that are respectively bent and parallel with one another,the second electrodes 36 are formed of a plurality of second thin metalwires 59 that are respectively bent and parallel with one another, andin the case in which the transparent conductive film is viewed from theviewing side, the plurality of first thin metal wires 58 and theplurality of second thin metal wires 59 overlap each other to form alarge number of meshes of polygons. In this case, it is preferable thata distance between adjacent first thin metal wires and a distancebetween adjacent second thin metal wires are 50 to 300 μm from theviewpoint of visibility.

In the case in which such first thin metal wire 58 and second thin metalwire 59 are used, it is possible to ensure excellent visibility with lowviewing angle dependency as in Embodiments 1 and 2.

In FIG. 8, as in FIG. 3, in order to easily distinguish the first thinmetal wire 58 and the second thin metal wire 59, the second thin metalwire 59 is indicated by a dotted line but is actually formed of aconnected wire like the first thin metal wire 58.

It is optimum to use the transparent conductive film according to thepresent invention for the touch panel shown in FIG. 1. However, thetransparent conductive film can be additionally applied to a heatgenerator for generating heat, an electromagnetic wave shield forshielding electromagnetic wave, and the like.

EXAMPLES

Hereinafter, the present invention is further specifically describedbased on examples. Materials, used amounts, ratios, the contents oftreatments, the treatment procedures, and the like illustrated in thefollowing examples may be appropriately changed unless the changedeparts from the spirit of the present invention. Thus, the scope of thepresent invention should not be interpreted in a limited manner based onthe examples illustrated below.

Example 1

As shown below, transparent conductive films having the configurationsshown in FIGS. 2 to 4 were produced.

First, a polyethylene terephthalate (PET) film having a thickness of 100μm was prepared as a transparent insulating substrate and an undercoatlayer having a thickness of 5 μm was formed on both surfaces of thetransparent insulating substrate by using a polyester resin. Further, anadhesion reinforcing layer having a thickness of 100 nm was formed onthese undercoat layers using silicon oxide formed by a sol-gel method.

Next, a blackened layer formed of copper oxide and having a thickness of0.1 μm was formed on the adhesion reinforcing layer positioned on therear surface of the transparent insulating substrate on the sideopposite to the viewing side by sputtering. Further, a copper layerhaving a thickness of 0.9 μm was formed on the adhesion reinforcinglayer on the front surface side of the transparent insulating substrateand a copper layer having a thickness of 1.4 μm was formed on theblackened layer on the rear surface side by sputtering and a blackenedlayer formed of copper oxide and having a thickness of 0.1 μm was formedon the copper layer on the front surface side by sputtering. Thus, alaminate in which the copper layer with the blackened layer was arrangedon each of the front surface and the rear surface of the transparentinsulating substrate was formed.

A resist was applied to each of the front surface and the rear surfaceof the laminate, and pre-baking was performed at a temperature of 80° C.for 30 minutes. Pattern exposure was performed on the resists on thefront surface and the rear surface of the laminate through respectivefirst exposure mask and second exposure mask made of quartz usingultraviolet rays while exposing both surfaces simultaneously. After theexposure, the resists were developed with alkali and patterned. Then,post-baking was performed at a temperature of 90° C. for 15 minutes andonly the resist on the front surface side of the laminate was furthersubjected to an annealing treatment using a halogen lamp to reinforcethe adhesion of the resist on the front surface side of the laminate.Thus, the adhesion of the resist on the front surface side of thelaminate was made stronger than the adhesion of the resist on the rearsurface side of the laminate.

The patterns on both surfaces of the laminate adopted a diamond-likemesh shape that is a mesh shape as shown in FIG. 3 and has a mesh pitchof 400 μm on each of the front surface and the rear surface of thelaminate and a narrow angle of the intersecting angle of 60 degrees. Aline width M1 of a first exposure mask for the first thin metal wire onthe viewing side was set to 3.0 μm and a line width M2 of a secondexposure mask for the second thin metal wire on the side opposite to theviewing side was also set to 3.0 μm.

With respect to the laminate having the patterned resists, copper andcopper oxide on both surfaces of the laminate were etched simultaneouslyby wet etching using an etching solution of an aqueous solution of iron(III) chloride at a temperature of 40° C.

Then, the resists were peeled off from both surfaces of the laminate,and the laminate was washed with water and dried. Thus, a transparentconductive film of Example 1 was produced.

Examples 2 and 3

Transparent conductive films of Examples 2 and 3 were respectivelyproduced in the same manner as in Example 1 except that the line widthM2 of the second exposure mask for the second thin metal wire on theside opposite to the viewing side was set to 2.5 μm and 2.2 μm.

Example 4

A transparent conductive film of Example 4 was produced in the samemanner as in Example 1 except that the line width M1 of the firstexposure mask for the first thin metal wire on the viewing side was setto 4.0 μm, and the line width M2 of the second exposure mask for thesecond thin metal wire on the side opposite to the viewing side was setto 4.0 μm.

Examples 5 and 6

Transparent conductive films of Examples 5 and 6 were respectivelyproduced in the same manner as in Example 4 except that the line widthM2 of the second exposure mask for the second thin metal wire on theside opposite to the viewing side was set to 3.5 μm and 3.2 μm.

Example 7

A transparent conductive film of Example 7 was produced in the samemanner as in Example 1 except that the thickness of the copper layer ofthe transparent insulating substrate on the viewing side was changed to1.9 μm, the thickness of the copper layer on the side opposite to theviewing side was changed to 2.9 μm, the line width M1 of the firstexposure mask for the first thin metal wire on the viewing side was setto 5.0 μm, and the line width M2 of the second exposure mask for thesecond thin metal wire on the side opposite to the viewing side was setto 5.0 μm.

Examples 8 and 9

Transparent conductive films of Examples 8 and 9 was respectivelyproduced in the same manner as in Example 7 except that the line widthM2 of the second exposure mask for the second thin metal wire on theside opposite to the viewing side was set to 3.5 μm and 3.2 μm.

Example 10

A transparent conductive film of Example 10 was produced in the samemanner as in Example 4 except that the thickness of the copper layer ofthe transparent insulating substrate on the viewing side was changed to0.4 μm and the thickness of the copper layer on side opposite to theviewing side was changed to 1.4 μm.

Example 11

A transparent conductive film of Example 11 was produced in the samemanner as in Example 4 except that the thickness of the copper layer ofthe transparent insulating substrate on the viewing side was changed to0.7 μm and the thickness of the copper layer on side opposite to theviewing side was changed to 1.4 μm.

Example 12

First, a polyethylene terephthalate (PET) film having a thickness of 100μm was prepared as a transparent insulating substrate, and an undercoatlayer having a thickness of 5 μm was formed on both surfaces of thetransparent insulating substrate using a polyester resin. Further, anadhesion reinforcing layer having a thickness of 100 nm was formed onthe undercoat layer positioned on the front surface of the transparentinsulating substrate on the viewing side using silicon oxide formed by asol-gel method.

Next, a copper layer having a thickness of 0.9 μm and a blackened layerformed of copper oxide and having a thickness of 0.1 μm weresequentially formed on the adhesion reinforcing layer by sputtering andthe copper layer with the blackened layer was formed on the frontsurface of the transparent insulating substrate.

Further, a resist was applied to the blackened layer and pre-baking wasperformed at a temperature of 80° C. for 30 minutes. Pattern exposurewas performed on the resist through a first exposure mask made of quartzusing ultraviolet rays. After the exposure, the resist was developedwith alkali and patterned. Then, post-baking was performed at atemperature of 120° C. for 1 hour to reinforce the adhesion of theresist.

As the pattern, a diamond-like mesh pattern that is a mesh pattern asshown in FIG. 3 and has a mesh pitch of 400 μm and a narrow angle of theintersecting angle of 60 degrees was adopted and a line width M1 of thefirst exposure mask was set to 3.0 μm.

The copper layer with the blackened layer in which the patterned resistwas arranged was etched by wet etching using an etching solution of anaqueous solution of iron (III) chloride at a temperature of 40° C.

Then, the resist was peeled off and the substrate was washed with waterand dried. Thus, a first thin metal wire having a reversely taperedshape was formed on the front surface of the transparent insulatingsubstrate.

Next, a release layer formed of polyolefin was formed on a surface of atransfer substrate made of glass and then a copper layer having athickness of 0.9 μm and a blackened layer having a thickness of 0.1 μmand formed of a copper oxide were sequentially formed on the releaselayer. Thus, the copper layer with the blackened layer was formed on thesurface of the transfer substrate.

A resist was applied to the blackened layer and pre-baking was performedat a temperature of 80° C. for 30 minutes. Pattern exposure wasperformed on the resist through a second exposure mask made of quartzusing ultraviolet rays. After the exposure, the resist was developedwith alkali and patterned. Then, post-baking was performed at atemperature of 120° C. for 1 hour to reinforce the adhesion of theresist.

As the pattern, a diamond-like mesh pattern that is a mesh pattern asshown in FIG. 3 and has a mesh pitch of 400 μm and a narrow angle of theintersecting angle of 60 degrees was adopted and a line width M2 of thesecond exposure mask was set to 2.5 μm.

The copper layer with the blackened layer in which the patterned resistwas arranged was etched by wet etching using an etching solution of anaqueous solution of iron (III) chloride at a temperature of 40° C.

Then, the resist was peeled off and the substrate was washed with waterand dried. Thus, a second thin metal wire having a reversely taperedshape was formed on the surface of the transfer substrate.

The second thin metal wire formed on the surface of the transfersubstrate was attached to the rear surface of the transparent insulatingsubstrate on the side opposite to the viewing side through a pressuresensitive adhesive layer and irradiation with ultraviolet rays wasperformed through the transfer substrate. The second thin metal wire wastransferred to the rear surface of the transparent insulating substrateand the transfer substrate was peeled off from the second thin metalwire. Thus, a transparent conductive film of Example 12 in which thesecond thin metal wire having a forward tapered shape on the rearsurface of the transparent insulating substrate was arranged wasproduced.

Comparative Example 1

A transparent conductive film of Comparative Example 1 was produced inthe same manner as in Example 1 except that the thickness of the copperlayer of the transparent insulating substrate on the side opposite tothe viewing side was set to 1 μm, the conditions for post-baking waschanged to a temperature of 120° C. for 1 hour, and further an annealingtreatment using a halogen lamp was not performed.

Comparative Example 2

A transparent conductive film of Comparative Example 2 was produced inthe same manner as in Example 1 except that the line width M1 of thefirst exposure mask and the line width M2 of the second exposure maskwere respectively set to 4.0 μm.

Comparative Example 3

A transparent conductive film of Comparative Example 3 was produced inthe same manner as in Example 1 except that the thickness of the copperlayer of the transparent insulating substrate on the viewing side andthe thickness of the copper layer of the transparent insulatingsubstrate on the side opposite to the viewing side were respectively setto 1.9 μm.

The cross section of each of the transparent conductive films ofExamples 1 to 12 and Comparative Examples 1 to 3 was observed using anelectron microscope and shown in FIG. 4, and the line width W1A of thefirst front surface 38A of the first thin metal wire 38 that wasdirected to the viewing side, the line width W1B of the first backsurface 38B that was directed to the side opposite to the viewing side,the line width W2A of the second front surface 39A of the second thinmetal wire 39 that was directed to the side opposite to the viewingside, and the line width W2B of the second back surface 39B that wasdirected to the side opposite to the viewing side were measured.

In addition, the viewing angle and the mesh visibility of each of thetransparent conductive films of Examples 1 to 12 and ComparativeExamples 1 to 3 were evaluated.

The measurement results and evaluation results thereof are shown inTable 1.

TABLE 1 Mask design Evaluation result value (μm) Measured value (μm)Viewing Mesh M1 M2 W1A W1B H1 W2A W2B H2 angle visibility EXAMPLE 1 3.003.00 2.98 2.06 1.0 2.99 3.96 1.5 B B EXAMPLE 2 3.00 2.50 2.96 2.01 1.02.56 3.52 1.5 B A EXAMPLE 3 3.00 2.20 2.98 2.04 1.0 2.28 3.22 1.5 B AEXAMPLE 4 4.00 4.00 3.96 3.01 1.0 4.08 3.10 1.5 B B EXAMPLE 5 4.00 3.503.98 3.04 1.0 3.62 2.64 1.5 B A EXAMPLE 6 4.00 3.20 3.98 3.06 1.0 3.342.26 1.5 B A EXAMPLE 7 5.00 5.00 5.01 2.98 2.0 5.11 2.96 3.0 B B EXAMPLE8 5.00 3.50 4.96 2.96 2.0 3.68 1.42 3.0 B A EXAMPLE 9 5.00 3.20 4.982.99 2.0 3.25 1.18 3.0 B B EXAMPLE 10 4.00 4.00 3.98 1.98 0.5 3.96 3.121.5 A A EXAMPLE 11 4.00 4.00 3.96 2.45 0.8 3.95 3.11 1.5 A A EXAMPLE 123.00 2.50 2.98 2.06 1.0 2.58 1.93 1.0 A A COMPARATIVE 3.00 3.00 3.012.08 1.0 2.10 2.98 1.0 C C EXAMPLE 1 COMPARATIVE 4.00 4.00 3.99 3.04 1.02.98 3.96 1.0 C C EXAMPLE 2 COMPARATIVE 5.00 5.00 4.99 3.01 2.0 2.964.98 2.0 C C EXAMPLE 3

The evaluation of the viewing angle was performed such that thetransparent conductive film was arranged on a horizontal black plate sothat the second thin metal wire was placed on the black plate side (onthe side opposite to the viewing side), white light was emitted to thetransparent conductive film from the upper side, and the transparentconductive film was visually observed at a height of 20 cm from thetransparent conductive film and two kinds of angles of 50 degrees and 30degrees respectively to evaluate whether or not the metallic luster ofthe transparent conductive film was observed.

In Table 1, the evaluation result A in the evaluation of the viewingangle refers to a level having an excellent viewing angle at which themetallic luster is not observed at both angles of 50 degrees and 30degrees, the evaluation result B refers to a level having no problem atwhich while metallic luster is not observed at an angle of 50 degrees,the metallic luster is slightly observed at an angle of 30 degrees, andthe evaluation result C refers to a level having a problem in viewingangle at which the metallic luster is observed at both angles of 50degrees and 30 degrees, respectively.

The evaluation of the mesh visibility was performed such that thetransparent conductive film was arranged on a horizontal black plate sothat the second thin metal wire was placed on the black plate side (onthe side opposite to the viewing side), white light was emitted to thetransparent conductive film from the upper side, and the transparentconductive film was observed at a depression angle of 45 degrees at twopoints of an observation point at a height of 40 cm from the transparentconductive film and an observation point at a height of 10 cm from thetransparent conductive film, respectively, to evaluate whether or notthe mesh pattern was observed.

In Table 1, the evaluation result A in the evaluation of the meshvisibility refers to a level exhibiting excellent visibility at which nomesh pattern is observed at both the observation point at a height of 40cm and the observation point at a height of 10 cm, and the evaluationresult B refers to a level having no practical problem in visibility atwhich while the mesh pattern is not observed at the observation point ata height of 40 cm, the mesh pattern is slightly observed at theobservation point at a height of 10 cm, respectively. In contrast, theevaluation result C refers to a level having a problem in visibility atwhich the presence of the first thin metal wire is noticeable at boththe observation point at a height of 40 cm, the observation point at aheight of 10 cm and the mesh pattern is apparently observed.

Regarding all of the transparent conductive films of Examples 1 to 12satisfying the relationship of Expression (1), that is,W1B<W1A and W2B<W2A,

it was confirmed that the evaluation results of the viewing angle were Bor higher and excellent visibility with low viewing angle dependency wasexhibited.

Further, it was confirmed that the transparent conductive films ofExamples 1, 4, 7, and 9 did not satisfy the relationship of Expression(2), that is,

0≤W1A−W2A≤0.3×W1A, and the relationship of Expression (3), that is,

W2A−W2B<W1A−W1B, and the evaluation results of the mesh visibility andthe evaluation results of the viewing angle were B. However, thevisibility and the metallic luster were at a level having no problem andpractical transparent conductive films could be obtained.

Among Examples 1 to 12, the transparent conductive films of Examples 2,3, 5, 6, and 8 were set to further satisfy the relationship ofExpression (2), that is,

0≤W1A−W2A≤0.3×W1A, and the evaluation results of the mesh visibilitywere A.

Both the transparent conductive films of Examples 10 and 11 were set tosatisfy the relationships of Expressions (1), (2), and (3), that is,

W2A−W2B<W1A−W1B, and the evaluation results of the mesh visibility andthe evaluation results of the viewing angle were A. It was confirmedthat transparent conductive films having excellent visibility with lowviewing angle dependency and not mesh visibility could be obtained.

In the transparent conductive film of Example 12 produced by usingtransfer, unlike other examples, although the thickness H2 of the secondthin metal wire was set to be equal to the thickness H1 of the firstthin metal wire, the relationships of Expressions (1), (2), and (3) weresatisfied. The evaluation result of the viewing angle and the evaluationresult of the mesh visibility were A. It was confirmed that atransparent conductive film having excellent visibility without viewingangle dependency and not mesh visibility could be obtained.

On the other hand, all of the transparent conductive film of ComparativeExamples 1 to 3 did not satisfy the above relationship of Expression (1)and the evaluation results of the viewing angle were C. Thus, it wasconfirmed that there was a problem in viewing angle dependency.

EXPLANATION OF REFERENCES

-   -   1: transparent insulating substrate    -   1A: front surface    -   1B: rear surface    -   2, 3: copper wiring    -   4: blackened layer    -   11: touch panel    -   12: support    -   13: transparent conductive film    -   14: adhesive    -   31: transparent insulating substrate    -   31A: front surface    -   31B: rear surface    -   32: conductive member    -   33: protective layer    -   34: first electrode    -   35: first peripheral wiring    -   36: second electrode    -   37: second peripheral wiring    -   38, 58: first thin metal wire    -   38A: first front surface    -   38B: first back surface    -   38C, 39C: side surface    -   39, 59: second thin metal wire    -   39A: second front surface    -   39B: second back surface    -   40, 41, 44: blackened layer    -   42: first metal layer    -   43: second metal layer    -   45: first resist layer    -   46: second resist layer    -   47: first exposure mask    -   48: second exposure mask    -   49: transfer substrate    -   50: release layer    -   S1: transmissive region    -   S2: peripheral region    -   D1: first direction    -   D2: second direction    -   W1, W2, W1A, W1B, W2A, W2B: line width    -   H1, H2: thickness

What is claimed is:
 1. A touch panel having a transmissive regioncomprising: a first electrode formed of first thin metal wires arrangedin the transmissive region; and a second electrode insulated from thefirst electrode and formed of second thin metal wires arranged tointersect the first thin metal wire in the transmissive region, whereinthe second thin metal wires is arranged on the side opposite to theviewing side than the first thin metal wires, the first thin metal wirehas a first front surface being directed to the viewing side and havinga line width W1A and a first back surface being directed to the sideopposite to the viewing side and having a line width W1B, the secondthin metal wire has a second front surface being directed to the viewingside and having a line width W2A and a second back surface beingdirected to the side opposite to the viewing side and having a linewidth W2B, the line widths W1A, W1B, W2A, and W2B are in a range of 0.5to 10 μm and satisfy a relationship ofW2A−W2B<W1A−W1B, and the line width W1A is larger than the line widthW1B and the line width W2A is larger than the line width W2B.
 2. Thetouch panel according to claim 1, wherein the line widths W1A and W2Asatisfy a relationship of0≤W1A−W2A≤0.3×W1A.
 3. The touch panel according claim 1, wherein athickness H2 of the second thin metal wire is larger than a thickness H1of the first thin metal wire.
 4. The touch panel according to claim 1,wherein the line width W1A is 1.5 μm or more and 5 μm or less, and thethickness H1 of the first thin metal wire and the thickness H2 of thesecond thin metal wire are 0.5 μm or more and 3 μm or less.
 5. The touchpanel according to claim 1, wherein the first front surface of the firstthin metal wire and the second front surface of the second thin metalwire are blackened layers.
 6. The touch panel according to claim 1,wherein the first thin metal wire and the second thin metal wire areformed of copper.